The Evolution of Coastal Erosion Control Technology – Part 1
The oceans are changing. Technological ingenuity is poised to meet the challenge.
With sea levels rising, coastal landmasses have been placed on a collision course with Mother Nature. Worldwide, coastal regions are highly populated, and coastal real estate is very desirable and very costly. At the same time, severe coastal storm events have resulted in loss of life and destruction of coastal structures and land masses.
Sea level rise history is very clear, and scientists worldwide are in agreement that this trend will continue. Globally, sea levels rose approximately 10 inches from 1880 to 2011. And, alarmingly, the rates are accelerating. Along the East Coast of the United States, for example, current sea level rise estimates vary, with a range of 1 to 5 feet predicted by the year 2100. Such projections are, of course, not popular. In some cases, reactions have included outright denial. However, the scientific community is in agreement that sea level rise will continue to threaten vulnerable coastal landmasses.
Coastal erosion, of course, is a natural and ongoing process. Our coastlines themselves have been carved and shaped by erosion. In addition to sea level rise and storm events, our coastlines are shaped by tidal action, rivers and streams, long-term erosion, geology, and human land management practices and intervention.
Against this backdrop, coastal erosion control practices and technology have moved more and more to the forefront. The demand for solutions has increased dramatically. Traditional practices have in many cases been called into question. Hard-armor solutions such as sea walls, groins, and revetments have been employed to mitigate coastal erosion for centuries. Such solutions have proved very effective in many cases. Unfortunately, these hard-armor structures can accelerate erosion or interfere with natural littoral drift or sand movement.
Without a doubt, coastal erosion control practices have been heavily influenced by the low-impact development movement. For years, land was developed with no regard for the impact on adjacent property. When large land areas were paved and covered with other impervious surfaces, the predictable result was increased site runoff volume and negative impacts on downstream real estate. Low-impact development stresses the need for more responsible site development with a goal of limiting discharges to historic levels. This can be done and is being done.
In effect, today’s land developers are asked to do the opposite of what they did 50 years ago. Yesterday’s goal was to drain all sites as quickly as possible; today’s is to slow down offsite flows to minimize their negative downstream impacts.
Therefore, it is not surprising that the most effective and promising coastal erosion control practices and technological innovations attempt to work in harmony with nature and not against it.
Sand Dunes
In 1969, the late Ian McHarg published Design With Nature, a book that today remains extremely influential with land-use planners. Of particular note is a chapter in the book titled “Sea and Survival.” In that chapter, the author describes natural processes that occur along seashores and the importance of close observation and study of natural processes. In his opening remarks, McHarg points out, “The people of the Netherlands have been engaged with the sea for two millennia.” Ultimately, he shows that the historic Dutch dikes are flexible and effective because they mimic the performance of natural sand dunes. McHarg adds, simply, “In their long dialogue with the sea, the Dutch have learned that it cannot be stopped but merely directed or tempered, and so they have always selected flexible construction.”
Modern designers have taken note, and sand dune preservation and restoration efforts have accelerated.
In an article published in Land and Water magazine (March/April 2013) titled, “A Dune, a Dune! My Kingdom for a Dune,” author Bill Young discusses the impact of Superstorm Sandy (October 29–30, 2012) on the New Jersey coastline. He discusses the areas of devastation and contrasted them with less impacted locations, stating, “Some areas right in the impact area were left less damaged. Less loss of property, less damage from flooding. They lost power and had some downed trees. These protected areas had one thing in common: dunes.”
In Design With Nature, describing another devastating New Jersey coastal storm event, McHarg had some particularly harsh words regarding land-use practices that preceded the storm. In his words, “While all the principles are familiar to botanists and ecologists, this has no effect whatsoever upon the form of development. Houses are built upon dunes, grasses destroyed, dunes breached for beach access and housing; groundwater is withdrawn with little control, areas are paved, bay shore is filled and urbanized.”
Overall, dunes provide much more than just a line of defense against coastal flooding. They provide nesting areas for migrating birds and food and habitat for countless other plant and animal species. And, as Young points out in his article mentioned earlier, the relatively low cost of dune creation and maintenance is dwarfed by the cost of restoring and reconstructing infrastructure in unprotected areas.
